The physical mounting and electrical connection of large and thus relatively heavy electrical devices, such as circuit interrupting devices, to switchboards is a rather difficult task. In some installations, physical mounting and electrical connection are commonly obtained using bolted joints at the device line terminals. In this way, the device is coincidentally supported by and electrically connected to the buswork of the switchboard. While this arrangement is quite effective in achieving both functions, the mounting and dismounting of the device is not particularly convenient. An additional, and quite significant disadvantage of bolted line terminals is that mounting and dismounting of the device is quite hazardous if performed while the switchboard is live. In many situations, it is impractical or at least undesirable to de-energize the switchboard, and thus the electricians must use insulative gloves and/or special tools.
To reduce the hazards of working with live switchboards, devices are provided with plug-in or stab-type terminal connectors which do not require manipulation during mounting and dismounting of the device. However, stab connectors are not capable of physically supporting large devices, which therefore must be somehow separately mounted to and supported by the switchboard. The separation of the electrical connection and physical mounting function renders this type of installation only somewhat more convenient to the electrician. Moreover, stab connections, particularly those having high current ratings, typically require considerable exertion by the electrician to effect connection and disconnection. This can be particularly unfortunate during disconnection, since the sudden release of stab connections can throw the electrician off balance, raising the possibility of personal injury, and damage to the device.
To alleviate this problem, special hand tools have been devised to pry the device from the switchboard to separate the stab connectors once the physical connection thereto has been broken. Alternatively, mechanical assists or so-called "racking mechanisms", such as disclosed in U.S. Pat. No. 3,142,003, have been devised for aiding the electrician in safely installing and removing devices from electrical switchboards. It will be appreciated that such prior art mechanical assist mechanisms, though desirable, add measurably to the cost of the equipment. A somewhat more practical arrangement has been proposed in U.S. Pat. No. 3,546,411 using a jackscrew approach. However, the jackscrews are physically disassociated from the device terminals.
It is accordingly an object of the present invention to provide an improved mechanical assist for facilitating the installation and removal of plug-in type electrical devices with respect to electrical panel assemblies.
An additional object of the present invention is to provide a mechanical assist of the above character which is incorporated in several of the electrical terminals of the device itself.
Yet another object of the present invention is to provide a mechanical assist of the above character which further serves the dual function of terminal electrical connection and physical support for the device.
Still another object of the invention is to provide a mechanical assist of the above character, which is readily compatible with existing designs for electrical devices and panel assemblies.
A further object is to provide a mechanical assist of the above character which is simple, inexpensive, reliable, and safe.
A still further object of the invention is to provide a multi-pole electrical device incorporating plural mechanical assists of the above character.
Other objects will in part be obvious and in part appear hereinafter.